The present invention relates to the technical field of a width measuring apparatus for measuring widths and changes of the width of an elongated object to be measured which travels at a high speed. More specifically, the present invention relates to the technical field of a tape width measuring apparatus for measuring that a wide tape raw material is slit to a predetermined width when it is slit by a slitter.
Conventionally, there are known magnetic tape slitter apparatuses for slitting a wide raw material to several tens of magnetic tapes to one hundred and several dozens of magnetic tapes, which are used in magnetic recording and reproducing apparatuses such as tape recorders, VTRs and the like and for winding them as respective magnetic tapes. Tape width measuring apparatuses for optically measuring changes of the width of a magnetic tape slit by a magnetic tape slitter apparatus have been known by Model ZDR, manufactured by Kosaka Kenkyusho and the like and described as prior arts in Japanese Unexamined Patent Publications Nos. 7-182724, 8-327330 and 8-327330.
However, since the tape width measuring apparatuses disclosed in Japanese Unexamined Patent Publications Nos. 7-182724 and 8-327330 are arranged to measure changes of the width of a tape which has been slit by a slitter apparatus and wound, independently of the slitter apparatus, they do not measure the width of the tape in a processing line just after it is slit by the slitter apparatus.
Further, Japanese Unexamined Patent Publication No. 8-327330 describes that xe2x80x9cwhile such a conventional measuring apparatus can be applied to existing magnetic tape width measuring apparatuses without any difficulty, it cannot be applied to a magnetic tape width measuring apparatus used for a magnetic tape having a higher signal recording density because the allowable range of the degree of straightness of the tape side edge thereof is narrower (a middle part of the sentence is omitted)xe2x80x9d. Thus, Model ZDR cannot be applied to the measurement of such a tape. xe2x80x9cAs to the cyclic changes of the degree of straightness of the tape side edge, since the conventional apparatus observes it at a cycle of about 100 mm along the tape side at the best, the apparatus is less reliable to the degree of straightness changes in a shorter cyclexe2x80x9d.
These conventional technologies can achieve relatively high measuring accuracy when the changes of the width, and the like of a tape, which is in a stationary state or travels slowly, are measured. However, it is difficult for the laser length measuring devices, which are used in these conventional technologies, to simultaneously measure a multiplicity of objects to be measured, which are located in a narrow region, such as magnetic tapes slit by a slitter from a wide raw material to several tens to one hundred and several dozens of tapes in a processing line. The reason is that the laser length measuring devices are considerably large in size. Accordingly, it is substantially impossible for the devices to continuously measure all the objects to be measured in a processing line.
The laser length measuring device (laser outside diameter measuring device) used as the tape width measuring apparatus is relatively expensive. Accordingly, an enormous expense is required to measure the width of respective tapes having been slit to several tens to hundred and dozens of pieces in the processing line. On the other hand, when less expensive laser elements and photodiodes are used, it is difficult to stably measure tape width because a measurement error is increased due to the thermal drift of output voltages caused by heat.
In addition, the laser length measuring device and, in particular, the laser outside diameter measuring device scan projected laser beams in the width direction of a tape. Thus, when the tape travels at a high speed, a tape width is measured at only two points in the scanning of the laser beams executed in one cycle. Therefore, the tape width is measured substantially in a sampling cycle and cannot be continuously measured. Moreover, in the tape traveling at the high speed, the width thereof cannot be correctly measured because the measuring points of the tape in lengthwise direction thereof are different on a right side edge and a left side edge of the tape.
A more appropriate technology has been desired for the measurement of a tape which travels at a high speed just after it is slit by a slitter apparatus.
A first object of the present invention is to eliminate the problems of the conventional technologies and to provide a width measuring apparatus which can continuously and optically measure the width of an elongated object to be measured in a non-contact fashion with a less amount of measuring error without using an expensive laser length measuring device, in particular, an expensive laser outside diameter measuring device, and to provide a width measuring apparatus, for example which can be applied in a slitter and the like used for magnetic tapes traveling at a high speed even if a multiplicity of the magnetic tapes, are located in a narrow region.
Further, a second object of the present invention is to eliminate the problems of the conventional technologies and to provide a width measuring apparatus which can be manufactured at a less expensive cost and can continuously and optically measure the width of an elongated object to be measured, for example, the width in a non-contact fashion with a less amount of error without using an expensive laser length measuring device, in particular, an expensive laser outside diameter measuring device while securing a working space where an operator can perform a job even if a multiplicity of the magnetic tapes, for example, are located in a narrow region.
To achieve the above first object, a first aspect of the present invention provides a width measuring apparatus which comprises; a light emitting element located on one side of a traveling elongated object to be measured for projecting. a laser beam over a range wider than a width of the elongated object to be measured in a width direction thereof; a pair of light receiving elements located on another side of the elongated object for respectively receiving each of a pair of partial laser beams of the laser beam at both edge portions of the laser beam from the light emitting element, the partial laser beams, passing by the elongated object without being shaded by the elongated object, and for detecting light quantities of the received partial laser beams; a measurement support table for fixing the light emitting element and the pair of light receiving elements as one set; and a calculating device for calculating the width of the elongated object from the light quantities received by the pair of light receiving elements.
It is preferable that the laser beam from the light emitting element is expanded in a fan shape.
The width measuring apparatus preferably comprises a calibration device for calibrating the light receiving elements, and more preferably the calibration device includes a calibration gauge having a predetermined width for calibrating the light receiving elements, in such a manner that after the light emitting element and the pair of light receiving elements are moved together to a calibrating position where the calibration gauge is disposed and positioned thereat, the light receiving elements respectively receive each of a pair of partial laser beams of the laser beam at both edge portions of the laser beam from the light emitting element, the partial laser beams, passing by the calibration gauge without being projected over the calibration gauge.
It is preferable that the calculating device measures the width of the elongated object to be measured by adding the respective light quantities received by the pair of light receiving elements.
Further the width measuring apparatus preferably comprises cupping removing bars for removing the cupping of the elongated object to be measured in travel, and provided forward and backward of the measurement support table, on which the light emitting element and the pair of light receiving elements are fixed, in the traveling direction of the elongated object to be measured.
And a first aspect of the present invention also provides: a width measuring apparatus, which comprises a plurality of sets of light emitting elements and pairs of light receiving elements, each set of which includes a light emitting element and pairs of light receiving elements in correspondence to an elongated object of a plurality of the elongated objects to be measured, wherein the light emitting element of is located on one side of the elongated object for projecting a laser beam over a range wider than a width of the elongated object to be measured in a width direction thereof, and the pair of the light receiving elements is located on located on another side of the elongated object for respectively receiving a pair of partial laser beams of the laser beam at both edge portions of the laser beam from the light emitting element, the partial laser beams, passing by the elongated object without being shaded by the elongated objects, and for detecting light quantities of the received partial laser beams; a measurement support table for fixing the sets of light emitting elements and pairs of light receiving elements in parallel with each other in correspondence to the respective ones of the plurality of the elongated objects which travel in parallel with each other; a calculating device for calculating the widths of the elongated objects from the light quantities received by the pairs of light receiving elements.
The width measuring apparatus preferably further comprises: a plurality of calibration devices, in correspondence to the pairs of light receiving elements, for calibrating the pairs of the light receiving elements.
It is more preferable that the calibration devices include calibration gauges having a predetermined width, for calculating the light receiving elements by using measured values of the calibration gauges, in such a manner that after the light emitting elements and the pairs of light receiving elements are moved together to calibrating positions in correspondence to the plurality of sets where the calibration gauges are disposed and positioned thereat, the light receiving elements respectively receive each of pairs of partial laser beams of the laser beams at both edge portions of the laser beams from the light emitting elements, the partial laser beams, passing by the calibration gauges without being projected over the calibration gauges. And more preferably, the elongated object to be measured is a magnetic tape just after slitting.
To achieve the above first object, a first aspect of the present invention provides a width measuring apparatus which comprises; a single light emitting element located on one side of a plurality of elongated objects to be measured for projecting laser beams which expand in the width direction of the elongated objects to be measured so that the laser beams are projected to the entire width of at least two of the elongated objects traveling in parallel with each other; a plurality of pairs of light receiving elements located on another side of the elongated objects to be measured in correspondence thereto for respectively receiving each of pairs of partial laser beams of the laser beam from the light emitting elements, the partial laser beams, passing by the elongated objects without being shaded by the elongated objects, and for detecting the light quantities of the received partial laser beams; a measurement support table for fixing the plurality of pairs of light receiving elements disposed in parallel with each other in the width direction of the elongated objects to be measured; and a calculating devices for calculating the widths of the plurality of elongated objects to be measured from the respective light quantities received by the plurality of pairs of light receiving elements.
It is preferable that the laser beam from the light emitting element is expanded in a fan shape. And that the distribution of luminance of the laser beams projected by the light emitting element in the width direction of the elongated objects to be measured is uniform.
It is preferable that the calculating device performs a correction due to a distribution of luminance of the laser beams in the width direction thereof, which expand in the width direction of the elongated objects, for correcting the values of the width of the elongated object to be measured by using luminance values obtained from the distribution of luminance and positions in the width direction of the light receiving elements.
The width measuring apparatus further comprises; calibration devices in correspondence to the plurality of the pairs of light receiving elements, for calibrating the light receiving elements, then the calibration devices includes a plurality of calibration gauges having a predetermined width, in correspondence to the plurality of the elongated objects, for calculating the light receiving elements, in such a manner that after the pairs of light receiving elements are moved together to calibrating positions respectively where the calibration gauges are disposed and positioned thereat, the pairs of light receiving elements respectively receive each of pairs of partial laser beams of the laser beams from the light emitting element, the partial laser beams passing by the calibration gauge without being projected over the calibration gauge, and it is more preferably, the calibration devices perform a correction due to a distribution of luminance of the laser beams in the width direction thereof, which expand in the width direction of the calibration gauges, for correcting the measured value of the width of the calibration gauges by using luminance values obtained from the distribution of luminance and positions in the width direction of the light receiving elements at the calibrating positions.
It is preferable that the calculating devices measures the widths of the elongated objects to be measured by adding the respective light quantities of the partial laser beams received by the pairs of light receiving elements.
And preferably the width measuring apparatus, further comprises; cupping removing bars for removing the cupping of the elongated objects to be measured in travel, and provided forward and backward of the measurement support table, on which the light emitting element and the pairs of light receiving elements are fixed, in the traveling direction of the elongated objects to be measured. It is preferable that the elongated objects to be measured are magnetic tapes just after slitting.